A plurality of methods for separating such a mixture of magnetizable and non-magnetizable particles are known and are briefly outlined here. Such methods are essentially based on the magnetic force that acts on magnetizable particles when a magnetic field gradient is present.
In known discontinuous methods, magnetizable isolation bodies such as iron wires, iron fibers or iron plates featuring surface structures such as slots or knobs, etc. in an external magnetic field generate a strong field gradient in their surroundings, wherein during an isolation phase said field gradient retains the magnetic particles of a suspension that flows past. In a second phase, the magnetic portion thus enriched is washed away in a subsequent rinsing step while the magnetic field is turned off. This method is disadvantageously discontinuous and requires the rinsing step.
In all known continuous methods, use is ultimately made of disadvantageous mechanically moving parts (for larger magnetizable particles in particular), wherein e.g. a magnet generates a magnetic field gradient on a surface of a rotating hollow cylinder, a disc or a conveyor belt. As a result of the movement, the surface travels beyond the magnetic field, such that the magnetizable portion then falls off or is stripped off. Separation of iron from refuse is one such example. The limited permissible distances between the magnet and the isolation surface represent a further disadvantage of these methods.
It was recently proposed, by means of a planar or cylindrical magnetic field generating means, to use a gradient field that deflects magnetizable particles toward at least one surface of a separating channel, such that magnetizable particles in a suspension flowing parallel with the magnetic field generating means in the separating channel are attracted and describe a path that is closer to the magnetic field generating means. A separated non-magnetic and magnetic material flow should then emerge via panels at the outlet. However, this approach is disadvantageous in a number of respects, since magnetic field and therefore magnetic force likewise are naturally stronger as a function of proximity to the field generating means, and therefore particles that are distant from the magnetic field generating means are deflected little, yet particles that are close to the magnetic field generating means are magnetically retained on the surface even despite the hydrodynamic forces of the flow. The separating effect is therefore reduced, and a rinsing step must also be used here to recover the magnetic portion after the magnetic field is turned off.